The kidneys are one of the most vital organs in the human body that are responsible for fluid regulation, filtration, and maintaining electrolyte levels. When your kidneys don’t work properly, toxins and excess fluids can build up in your body, leading to serious health issues. This is why Kidney Function Tests are important. 

In this blog, we’ll discuss everything you need to know about kidney function tests, from what they are and why they matter to how they’re conducted and how to interpret the results. 

What are Kidney Function Tests?

Kidney function tests include a number of blood and urine tests that help in analysing the functioning of the kidneys. It is used to measure kidney health, such as how effectively they are filtering waste, balancing fluids, and maintaining electrolyte levels. The test results are used by the doctors to diagnose kidney conditions, to check the progression of the diseases, and to evaluate the effectiveness of treatment plans. These tests consider the levels of waste products like urea and creatinine, electrolytes like Sodium, Potassium, Calcium Phosphorus and proteins in the urine.

Why Kidney Tests are Necessary?

Many of the kidney diseases and problems develop slowly and don’t show any signs until the condition has advanced. Early detection through kidney function tests can help prevent further complications. Conditions like diabetes and high blood pressure are some of the main causes of kidney damage. So, testing regularly helps mitigate complications. These tests also help doctors to adjust the medications and lifestyle and decide on the necessity of dialysis. 

What Are the Types of Kidney Function Tests?

Two main types of tests and urine test, are used to measure different aspects of kidney health. 

• Blood Urea (BU)

The Blood Urea test is carried out to measure the amount of urea, a waste product, in the bloodstream. Urea, formed during the process of protein breakdown, is typically filtered out by the kidneys. High levels of BU in the blood can indicate that the kidneys are not working properly. However, BU levels can also be affected by other factors like dehydration, a high-protein diet, or certain medications, so it is often interpreted in conjunction with other tests like the creatinine test.

• Serum Creatinine

Creatinine is a waste product from the normal wear and tear of muscle tissue. It is produced at a relatively constant rate and is almost entirely filtered out of the blood by the kidneys. The serum creatinine test measures the level of creatinine in the blood. Since the body produces creatinine at a steady rate, a high level in the blood is a strong indicator that your kidneys are not filtering it out efficiently, a sign of kidney damage.

• Estimated GFR (eGFR)

The Estimated Glomerular Filtration Rate (eGFR) is consideredas one of the best tests to understand kidney function. The glomeruli are tiny filters in your kidneys that clean your blood. The GFR measures how much blood passes through these filters per minute. An eGFR is an estimate based on your blood creatinine level, age, sex, and race. It is a simple and non-invasive way to get a clear idea of your kidney’s filtering capacity. A healthy GFR is typically 90 or higher.

• Microalbuminuria

This is a urine test that checks for the presence of albumin, a protein, in your urine. Healthy kidneys prevent albumin from passing from the blood into the urine. Even a small amount of albumin in the urine, a condition known as microalbuminuria, can be one of the earliest signs of kidney disease, especially in people with diabetes or hypertension.

• Urinalysis

A urinalysis is a comprehensive test that examines a urine sample for various substances. It can detect the presence of protein, blood, white blood cells, and other markers. It can help diagnose a wide range of conditions, including glomerulonephritis, urinary tract infections (UTIs), and even diabetes. A urinalysis can be a simple, routine part of a health check-up.

How the Tests are Performed

Kidney function tests are easy to carry out with minimal preparation. They involve collecting either a blood sample or a urine sample.

• 24-hr Urine Sample

This test provides a more comprehensive look at your kidney function over a full day. You will be given a container to collect all of your urine for a 24-hour period. You'll be instructed to collect all urine passed during the day, storing the container in a cool place, like a refrigerator. After the 24-hour period, you will return the sample to the lab for analysis. This method is particularly useful for measuring the total amount of protein or other substances excreted in your urine throughout a day.

• Blood Samples

A blood test for kidney function is quick and simple. A healthcare professional, called a phlebotomist, will draw a blood sample, usually from a vein in your arm. The process takes only a few minutes. You may be required to fast for a certain period before the test, and your doctor will inform you of any other specific instructions, such as avoiding certain foods or medications.

Results and Follow-Up

Understanding the results of your kidney function tests is crucial for maintaining your health. Your doctor will interpret the results in the context of your overall health, age, and medical history.

• What do the results of my kidney function test mean?

The results of your kidney tests indicate how well your kidneys are filtering waste and maintaining electrolyte balance. Abnormal results may suggest kidney disease, dehydration, infection, or other underlying conditions.

• Estimated glomerular filtration rate

The eGFR result is often a key focus. The value is a number that represents a percentage of your total kidney function. A higher number is better. The stages of chronic kidney diseases: 

• Stage 1: Normal eGFR: 90 mL/min/1.73m² or higher
• Stage 2: Mildly decreased function: 60–89 mL/min/1.73m²
• Stage 3: Moderate impairment: 30–59 mL/min/1.73m²
• Stage 4: Severe impairment: 15–29 mL/min/1.73m²
• Stage 5: Kidney failure (end stage if kidney disease): Less than 15 mL/min/1.73m²

• Interpretation of the eGFR value

• Above 60: Generally considered normal, unless other markers show abnormality.
• Below 60: Indicates possible chronic kidney disease.
• Below 15: Suggests kidney failure, requiring dialysis or transplant evaluation.

• Urine albumin-creatinine ratio

The Urine albumin-creatinine ratio (uACR) is a simple way toidentify kidney damages. A normal uACR is less than 30 mg/g. A ratio between 30 mg/g and 300 mg/g indicates microalbuminuria, a sign of early kidney disease. A ratio over 300 mg/g is a sign of macroalbuminuria and more advanced kidney damage. The higher the ratio, the more serious the kidney damage.

When to See a Doctor?

Kidney diseases can often progress without any signs or symptoms in its early stage. Therefore, regular testing is important. However, if you experience any of the following symptoms, you should consult a doctor immediately:

• Frequent urination, especially at night, or reduced urine output.
• Swelling in your ankles, feet, hands, or face, often a sign of fluid retention.
• Extreme tiredness and lack of energy.
• A buildup of toxins can cause nausea and vomiting.
• You may feel full or have a metallic taste in your mouth, with loss of appetite.
• A buildup of waste products in your blood can cause severe itching.
• Electrolyte imbalances can lead to muscle spasms.

Test Your Kidneys' Functioning with Amrita Hospital, Kochi

Your kidneys play a vital role in keeping your body balanced and healthy, and regular check-ups can help identify problems before they become serious. At Amrita Hospital, Kochi, you get access to advanced diagnostic facilities, expert nephrologists, and a patient-centered approach to care. Whether it’s a routine kidney function test or specialised treatment, our team ensures accurate results and timely guidance.

Book your kidney function test at Amrita Hospital, Kochi, and give your body the care it deserves.

Frequently Asked Questions

1. What is the basic test for kidney function?

Basic kidney function tests include blood and urine sample testing to evaluate the kidneys' efficiency in filtering waste, maintaining the fluid balance, and electrolyte balance. Most commonly conducted blood tests include creatinine, blood urea nitrogen (BUN), and estimated glomerular filtration rate (eGFR). The albuminuria test is an important urine test done to check the protein content in urine. 

2. What are the signs of poor kidney function?

Some of the most common symptoms of poor kidney function are swollen feet and ankles, persistent fatigue, dry and itchy skin, diseased urine output, muscle cramps, nausea and vomiting, difficulty in concentrating, and a general feeling of weakness. 

3. What damages the kidney the most?

Common contributors to kidney disease include diabetes and high blood pressure. Uncontrolled diabetes can cause high blood sugar levels (hyperglycemia), which can damage the vital organs, including the kidneys. 

4. How to improve kidney function?

Controlling blood pressure and blood sugar, adopting a heart-healthy, low-sodium diet, maintaining a healthy weight, engaging in regular physical activity, and avoiding smoking and drinking can improve kidney health to a great extent. Conducting regular check-ups and limiting the use of over-the-counter pain relievers are also advised by the doctors.